KR101313439B1 - Titanium plate - Google Patents

Abstract

This invention aims at providing the titanium plate which is high strength and is excellent in workability. For solving the above problems, by mass, the iron content is more than 0.10% and less than 0.60%, the oxygen content is more than 0.005% and less than 0.10%, the carbon content is less than 0.015%, the nitrogen content is less than 0.015%, The content of hydrogen is less than 0.015%, and the remainder consists of titanium and an unavoidable impurity, the two-phase structure of (alpha) phase and (beta) phase is formed, and it is formed so that the average particle diameter per circular phase of the said β phase may be 3 micrometers or less. Provide a titanium plate.

Description

Titanium plate {TITANIUM PLATE}

The present invention relates to a titanium plate, and more particularly, to a titanium plate excellent in workability.

Conventionally, titanium materials such as titanium alloys and pure titanium are generally lighter and higher in strength than iron-based materials such as iron or their alloys. Therefore, sports and leisure equipment, medical equipment, members for various plants, aerospace and aerospace relations It is widely used in equipment and the like.

Moreover, since titanium material is excellent also in corrosion resistance etc., it is used for the plate material of a plate heat exchanger, the muffler member of a motorcycle, etc., for example.

When manufacturing such a product, the various processes which carry out plastic deformation, such as a bending process and a drawing process, are performed to the board (titanium board) formed with the titanium material, for example.

Therefore, in order to provide for such various uses, the titanium plate has been requested | required to have the outstanding workability with respect to shaping | molding processes, such as drawing process.

However, in recent years, as a result of thinning of the titanium plate in order to reduce the material cost and the like, there has been a demand for improvement in strength.

In other words, there has been a demand for simultaneously satisfying the characteristics in the trade-off between formability and strength.

Sponge titanium, which is a raw material of the titanium plate or the like, is produced by the crawl method. For example, pure titanium is produced by a method of obtaining an ingot by arc dissolving the sponge titanium obtained by the crawl method. .

Pure titanium is classified according to the content of iron and oxygen other than titanium in the Japanese Industrial Standard (JIS), and JIS 1 type, JIS 2 type, JIS 3 type, JIS 4 type, etc. are prescribed by JIS.

As these material characteristics, JIS1 type with little content, such as iron, is the lowest strength and is excellent in moldability.

And it is known that it becomes high strength as it becomes JIS2 type and JIS3 type.

On the other hand, as it becomes JIS2 type | system | group and JIS3 type | mold, moldability falls, and it is not easy to apply drawing processing etc. to the titanium plate which consists of these, and to obtain a favorable molded article.

In contrast, Patent Literatures 1 to 3 disclose that the content of components other than titanium, such as iron, in a titanium material is controlled in a predetermined or less range to improve moldability.

However, what is described in such a patent document cannot expect sufficient intensity | strength.

Moreover, since the reduction reaction in the said crawling method is normally performed discontinuously (batchwise) in a carbon steel or an iron alloy container, in the sponge titanium of the site | part near the container side among the obtained sponge titanium, a container It contains more iron than sponge titanium in the area near the center.

For this reason, when iron content is limited to the range of 0.035%-0.100% like patent document 3, titanium in the center of a container must be used, and there exists a possibility that a used material may become limited and it may become expensive.

In addition, although the following patent documents 4 and 5 allow more iron containing than the invention of patent documents 1-3, it cannot be said that it has sufficient moldability.

Patent Document 1: Japanese Unexamined Patent Publication No. 63-60247 Patent Document 2: Japanese Patent Application Laid-Open No. 9-3573 Patent Document 3: Japanese Unexamined Patent Publication No. 2006-316323 Patent Document 4: Japanese Unexamined Patent Publication No. 2008-127633 Patent Document 5: Japanese Unexamined Patent Publication No. 2002-180166

This invention aims at providing the titanium plate which is high strength and is excellent in workability.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the said subject, by forming a titanium plate so that iron and oxygen may be a predetermined content, and a crystal grain may become a predetermined state, this inventor can form a titanium plate with high strength and excellent workability. It has been found that the present invention has been completed.

That is, the present invention relates to a titanium plate for solving the above problems, in terms of mass, the iron content is more than 0.10% and less than 0.60%, the oxygen content is more than 0.005% and less than 0.10%, and the carbon content is less than 0.015%. , The nitrogen content is less than 0.015%, the hydrogen content is less than 0.015%, the balance is made of titanium and unavoidable impurities, the two-phase structure of α and β phases are formed, and the average particle diameter of the equivalent of the β phase is 3 μm or less It is characterized in that it is formed to be.

According to the present invention, a titanium plate having high strength and excellent workability can be provided.

1 is a micrograph showing the microstructure of the titanium plate of Example 7. FIG.
Fig. 2 is a graph showing the relationship between the average equivalent particle size of the β phase and the Eriksen value.

EMBODIMENT OF THE INVENTION Below, preferable embodiment of this invention is described.

The titanium plate in this embodiment is formed of the titanium material containing the following components, and is formed so that the two-phase structure of the alpha phase and the beta phase is formed, and the average particle diameter per circle of the beta phase is 3 μm or less. have.

In the titanium material, the content of iron (Fe) is more than 0.10% and less than 0.60%, the content of oxygen (O) is more than 0.005% and less than 0.10%, the content of carbon (C) is less than 0.015%, nitrogen The content of (N) is less than 0.015%, the content of hydrogen (H) is less than 0.015%, and the balance is made of titanium (Ti) and unavoidable impurities.

As described above, the iron (Fe) is contained in the titanium material in a content of more than 0.10% by mass and less than 0.60%.

Fe is a β-stabilizing element, and most of the solid solution forms a β-phase.

In addition, Fe exists as TiFe by heat processing etc., and it is known to inhibit growth of a crystal grain.

For this reason, conventionally, when the Fe content of the titanium material is increased, the grain size of the α phase formed on the titanium plate is reduced, and the ductility (molding processability, etc.) of the erysene value such as the strength of the titanium material and the workability of polishing can be improved. ) Was considered to be deteriorating.

However, as described later, even if the Fe content in the titanium plate is increased, by adjusting the size of the β phase to a predetermined value with the O content as a predetermined value, the strength can be improved while suppressing the decrease in the ductility. have.

The Fe content in the titanium material forming the titanium plate of the present embodiment exceeds 0.10% by mass and is less than 0.60%, when the Fe content is 0.10% or less, sufficient strength for the titanium plate to be formed. This is because there is a risk that can not be granted.

On the other hand, when the content is 0.60% or more, even if the O content in the titanium material is a predetermined value, ductility decreases, and there is a possibility that the moldability of the titanium plate may be reduced.

In addition, in the crawling method, normally, the titanium material which shows iron content of 0.60% or more forms only a very small area | region near the container.

Therefore, since the upper limit of content of iron is 0.60 mass% as the component in the titanium plate in this embodiment, most of the sponge titanium obtained by the crawl method can be used as a raw material.

That is, since the titanium plate of this embodiment is easy to obtain, it can be said that it is suitable as a consumer goods used for formation of a molded article.

The oxygen (O) is contained in the titanium material in a content of more than 0.005% by mass and less than 0.10%.

The O content in the titanium material forming the titanium plate of the present embodiment exceeds 0.005% by mass and is less than 0.10%. When the O content is 0.10% or more, the strength of the titanium plate is too improved, and the β-phase It is because there exists a possibility that molding processability may not become favorable even if it adjusts.

Moreover, it is important to make carbon (C), nitrogen (N), and hydrogen (H) below content equivalent to JIS2 type from the objective of ensuring the favorable workability in shaping | molding process.

More specifically, it is important to make content of C, N, and H into less than 0.015% by mass, respectively.

Moreover, it is preferable to make content of C into 0.01% or less, content of N into 0.01% or less, and content of H into 0.01% or less.

From a viewpoint of the workability of a titanium plate, although a lower limit is not set to content of said C, N, H, when it is going to reduce such content extremely, there exists a possibility that the manufacturing cost of a titanium plate may increase significantly.

From a viewpoint of suppressing such a cost up, it is preferable to make C content into 0.0005% or more, content of N into 0.0005% or more, and content of H into 0.0005% or more.

Conventionally, the titanium plate which requires favorable workability in molding is usually a single phase because a titanium material having a small iron content equivalent to JIS type 1 or JIS type 2 is used.

The larger the size of the α particle size is, the more excellent the formability is. Therefore, it is important that the titanium plate in the present embodiment has a two-phase structure of α + β, but the average particle diameter of the equivalent phase of the β phase is 3 μm or less. Do.

By forming a titanium plate so that it becomes such a structure, the index which shows workability, such as an Eriksen value, can be improved.

If the average equivalent particle diameter of the β-phase exceeds 3 µm, the Ericsen value may be lowered, for example, to less than 10 mm.

This is because cracking due to stress concentration tends to occur at the boundary between the coarse β-phase and α-phase, thereby degrading the workability of the titanium plate.

The lower limit of the average equivalent particle size of the β phase is not particularly determined. However, in order to obtain a titanium plate of less than 0.05 μm, the production cost may be greatly increased.

In addition, about the circular equivalent average particle diameter of this (beta) phase, it can obtain | require by the method as described in the "Example" of the following stage.

In addition, this knowledge was discovered by the present inventors by the following method.

That is, in a small vacuum arc melting furnace, using a plurality of kinds of titanium materials having different iron contents, 0.5 mm thick cold rolled sheet is started while changing the annealing conditions, and the formability of the obtained cold rolled sheet (titanium sheet) is Eriksen It evaluated by the test (detail is described in the following "Example").

For example, it was found that when the annealing time is lengthened, the particle size of the β phase increases, and the Ericsen value decreases as the particle size of the β phase increases.

In addition, when the structure and the wavefront were examined in detail, cracks were found at the interface between the coarse β grains and the α phase. As a result, the grain size of the β phase was reduced by changing the annealing conditions.

In particular, it was found that a high-strength titanium plate excellent in workability was obtained when the average equivalent particle diameter of the β phase was 3 µm as the boundary.

As indicated by the description of the process of obtaining this knowledge, the size of the particle size of the β phase can be adjusted by the iron content in the titanium material, the finish annealing temperature and the finish annealing time during the production of the titanium plate.

Below, such conditions in a titanium plate manufacturing method are demonstrated.

Under the conditions of the finish annealing temperature and finish annealing time at the time of titanium plate manufacture, by lowering the finish annealing temperature, the growth of β grains can be suppressed and the crystal grain size can be made small.

In addition, by shortening the annealing time, it is possible to suppress the growth of crystal grains and to reduce the crystal grain size.

More specifically, when the finish annealing temperature is less than 550 ° C., there is a fear that the workability after cold rolling does not recrystallize and the moldability is lowered.

On the other hand, when such temperature exceeds 800 degreeC, iron diffusion in titanium may accelerate and crystal grains of (beta) phase may coarsen.

From this point of view, the finish annealing temperature is preferably in the range of 550 ° C or more and 800 ° C or less.

The finish annealing time is determined by the finish annealing temperature, the plate thickness of the titanium plate, the capacity of the annealing furnace, and the like.

That is, when finishing annealing temperature is 650 degreeC or more and 800 degrees C or less, it is preferable that finishing annealing time exceeds 0 minutes and is 15 minutes or less.

In addition, even when the finish annealing is completed immediately after the temperature of the titanium plate reaches the finish annealing temperature, there is a low possibility that the formability is lowered if the finish annealing time exceeds 0 minutes even if the tissue causes recrystallization during heating. .

On the other hand, the upper limit of the finish annealing time is 15 minutes at the finish annealing temperature because the finish annealing for more than 15 minutes causes the β phase crystal grains to coarsen and deteriorate the workability of the titanium plate.

Moreover, when finish annealing temperature is 550 degreeC or more and less than 650 degreeC, when annealing time is t (minute) and annealing temperature is T (degreeC), it is preferable to perform finish annealing so that following formula (1) may be satisfied. .

In this temperature range, the recrystallization proceeds, but the speed is slow, so that some time required for recrystallization is required.

And by selecting conditions which satisfy | fill the said Formula (1), the moldability improvement by recrystallization can be aimed at.

However, in the case where the finish annealing temperature exceeds 630 ° C. and less than 650 ° C., if the annealing is performed for a long time, the crystal grains of the β phase may coarsen and deteriorate the workability of the titanium plate.

For this reason, in this temperature range, it is preferable to perform finish annealing so as to satisfy following formula (2).

Moreover, when finishing annealing temperature is the temperature within the range of 550 degreeC or more and 630 degrees C or less, it is preferable that annealing time shall be 300 minutes or less.

By selecting such conditions, coarsening of the β phase in the structure formed on the titanium plate can be suppressed, and good workability can be imparted to the titanium plate.

In addition, if the finishing annealing time of more than 300 minutes is set within this temperature range, the crystal grains of the β phase are coarsened, which may lower the workability of the titanium plate.

By employing the above-described manufacturing conditions, the particle size of the β phase in the titanium plate can be adjusted to a predetermined value or less, and a titanium plate excellent in strength and workability can be obtained.

In addition, although it is not mentioned here, it is possible to employ | adopt the well-known matter in the conventional titanium plate and the titanium plate manufacturing method in the titanium plate of this embodiment in the range which does not impair the effect of this invention remarkably.

Example

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

(Examples 1-22, Comparative Examples 1-3)

(Production of a test piece)

Ingot (φ140mm) was produced by small vacuum arc melting, and after heating this ingot to 1150 degreeC, the slab of thickness 50mm was produced.

After hot-rolling this slab to 5 mm in thickness at 850 degreeC, it annealed at 750 degreeC and cut the scale of the surface, and produced the board | plate material of thickness 4mm.

The plate was cold rolled to prepare a plate-shaped sample (titanium plate) having a thickness of 0.5 mm.

About the titanium plate whose thickness is 0.5 mm, the finish annealing in the vacuum atmosphere was performed and the test piece for evaluation was produced.

In this finishing annealing, the grain size of the said test piece was adjusted by adjusting the temperature (550 degreeC or more and 800 degrees C or less) and time (300 minutes or less).

(Component measurement)

The iron amount and oxygen amount contained in a titanium plate were measured using the board | plate material whose thickness of the surface cut off was 4 mm.

Iron content was measured according to JIS H1614, and oxygen content was measured according to JIS H1620.

Tensile strength measurement

In addition, the tensile strength of the test piece (titanium plate) with the crystal grain adjusted as described above was measured according to JIS Z 2241.

(Processability evaluation)

Moreover, the Ericsen value of the test piece (titanium plate) with which the crystal grain size was adjusted as mentioned above was measured according to JIS Z2247, and the workability of a titanium plate was evaluated.

(Tissue investigation)

The aspect which observed the microstructure of the titanium plate by the microphotograph is shown in FIG. 1 (microstructure of Example 7).

In this structure photograph, since the β phase comes out black and the α phase comes out white, this image is binarized using image analysis software to obtain an average area of the β phase, and to calculate the diameter of a circle having the same area as the average area. Obtained by the average equivalent diameter.

The above result was shown in Table 1.

Examples 1 to 4 and Comparative Example 1 in Table 1 have the same iron content and oxygen content, but the average particle diameter of the equivalent of β phase is adjusted according to the difference in annealing conditions, and the average particle diameter of the equivalent of β phase is small. The higher the Eriksen value.

In addition, the same tendency is seen in other examples and comparative examples, and from Fig. 2 showing the relationship between the average equivalent particle diameter of the β phase and the Eriksen value in Table 1, it is high strength according to the present invention. It was found that a titanium plate excellent in workability can be provided.

Claims (1)

By mass, iron content exceeds 0.10% and less than 0.60%, oxygen content exceeds 0.005% and less than 0.10%, carbon content less than 0.015%, nitrogen content less than 0.015%, and hydrogen content less than 0.015% Wherein the remainder is made of titanium and unavoidable impurities, and a two-phase structure of the α and β phases is formed, and the titanium plate is formed such that the average particle diameter of the equivalent of the β phases is from 0.05 µm to 3 µm.

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